The invention relates to a method of triggering a warhead in target-tracking guided missiles, which have an impact fuse and a proximity fuse for triggering a warhead.
Furthermore the invention relates to a device for triggering a warhead in target-tracking guided missiles, which have an impact fuse and a proximity fuse for triggering a warhead, the proximity fuse triggering the warhead with a warhead triggering delay time.
Target tracking guided missiles usually have an impact fuse trigger and a proximity fuse trigger for triggering a warhead. The proximity fuse trigger triggers the warhead with a delay time, herein called xe2x80x9cwarhead triggering delay timexe2x80x9d.
Target-tracking guided missiles are guided to a target by means of a seeker head. Usually, such seeker head comprises an image-resolving detector, conventionally a two-dimensional array of detector elements. The picture thus obtained of a scenario containing the target is applied to image processing means. Guidance signals are derived from the image processing, the missile being guided to the target by these guidance signals. When the missile more closely approaches the target, the seeker head will provide an image of the target, which becomes the larger the smaller the distance to the target is.
The guided missile contains a warhead, i.e. an explosive charge, and the target is to be destroyed by this explosive charge with maximum probability. The trajectory of the guided missile may deviate from the ideal trajectory due to various influences. This deviation may be due, for example, to the relative geometry of missile and target, if the target makes an evasive maneuver, to inaccuracies of the guidance of the guided missile, or to limitations of the maneuverability of the guided missile. In such case, the guided missile will not hit the target at the optimal aim point. The guided missile may even miss the target at a more or less large distance. The guided missile has an impact fuse trigger. The impact fuse trigger triggers the warhead, when the guided missile hits the target directly. Furthermore, the guided missile has a proximity fuse trigger. The proximity fuse trigger responds, when the guided missile has approached the target sufficiently. The proximity fuse trigger will trigger the warhead even if the guided missile misses the target. Triggering is effected with a warhead triggering delay time, after the proximity fuse trigger has responded. The warhead triggering delay time is selected such that the warhead, during the passage past the target, is triggered at a moment, when the detonating warhead and the fragments blasted off cause maximum damage to the target. Conventionally, the warhead triggering delay time is a fixed, empirically found value.
It is an object of the invention, to trigger the warhead of a guided missile such that maximum damage to the target is caused.
To this end, influencing variables are detected which influence the type of encounter of the guided missile with the target, and the warhead triggering delay time is set depending on such influencing variables. Preferably, a miss distance is predicted from influencing variables detected during the flight. The warhead triggering delay time of the proximity fuse is set depending on the miss distance thus predicted.
Accordingly, the guided missile contains means for detecting influencing variables influencing the miss distance during the flight of the guided missile means for determining a predicted miss distance from theses influencing variables and setting means for setting the warhead triggering delay time depending on the miss distance thus predicted.
If the image of a target such as a fighter aircraft is considered, a desired aimpoint can be defined thereon, in which the target ought to be hit by the guided missile to ensure maximum destructive effect of the warhead. Starting from this desired aimpoint, miss distances can be defined with regard to amount and direction of the miss. In accordance with the basic concept of the invention, this miss distance is predicted depending on various observable influencing variables. The warhead triggering delay time is set as a function of this predicted miss distance.
This can be done, for example, by setting a long warhead triggering delay time, if the predicted miss distance permits a direct hit to be anticipated, whereby the warhead will be triggered by the impact fuse upon impact of the guided missile on the target. If, however, the predicted miss distance lets a passage of the guided missile past the target to be expected, a warhead triggering delay time will be set which is optimized with regard to the efficiency of the detonating warhead.
The relation between the miss distance and both the influencing variables and the time-to-go can be derived by simulation and can be stored.
Influencing variables may be guidance-specific variables, such as the sight line rate, which result from the geometry of target and guided missile. The influencing variables may, however, also be missile-specific variables, such as control surface deflection or lateral acceleration. These influencing variables become effective, above all, if the guided missile gets near its limits of maneuverability.
The time-to-go can be derived from the image processing of a target image provided by an image resolving seeker head of the guided missile. Preferably, however, a predicted miss distance is continuously determined for a certain selected time-to-go. The miss distance predicted in this way for a selected time-to-go is output for determining the warhead triggering delay time with a delay equal to this selected time-to-go, when the proximity fuse responds.
Influencing variables, such as the sight line rate, are continuously determined. On the basis of these influencing variables, the predicted miss distances are computed for a selected time-to-go. The miss distances thus computed or determined are output with a delay equal to the time-to-go on which the computation or other determination was based. Thus, when the proximity fuse responds, predicted miss distances are available which were measured the selected time-to-go ago and now refer to the moment at which the proximity fuse responds. Thus no time-to-go estimates are necessary. Such estimation would usually be rather inaccurate.
Such a miss distance based on one single time-to-go may be corrupted by noise. Therefore, advantageously, predicted miss distances are determined from the influencing variables in parallel for different times-to-go. Each of these miss distances determined for an associated time-to-go is made available for the determination of the warhead triggering delay time, when the proximity fuse responds, delayed by this associated time-to-go. An average or weighted average of the predicted miss distances output with time delay is used to determine the warhead triggering delay time.
An embodiment of the invention is described hereinbelow with reference to the accompanying drawings.